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GREGG Gregg in Situ <br /> Environmental and Geotechnical Site Investigation Contractors <br /> ' Gregg In Situ CPT Interpretations as of January 7, 1999 (Release 100 19) <br /> Gregg In Situ's Interpretation routine should be considered a calculator of current published CPT <br /> correlations and is subject to change to reflect the current state of practice The interpreted values are not <br /> considered valid for all soil types The interpretations are presented only as a guide for geotechnical use <br /> and should be carefully scrutinized for consideration in any geotechnical design Reference to current <br /> ' literature is strongly recommended <br /> The CPT Interpretations are based on values of tip, sleeve friction and pore pressure averaged over a <br /> user specified Interval (typically 0 25m) Note that Qt is the recorded tip value, Qc, corrected for pore <br /> pressure effects Since all Gregg In Situ cones have equal end area friction sleeves, pore pressure <br /> corrections to sleeve friction, Fs, are not required <br /> The tip correction is Qt= Qc*(1-a) .Ud <br /> ' where Qt is the corrected tip load <br /> Qc is the recorded tip load <br /> Ud is the recorded dynamic pore pressure <br /> ' a Is the Net Area Ratio for the cone(typically 0 85 for Gregg In Situ cones) <br /> Effective vertical overburden stresses are calculated based on a hydrostatic distribution of equilibrium <br /> pore pressures below the water table or from a user defined equilibrium pore pressure profile(this can be <br /> obtained from CPT dissipation tests) The stress calculations use unit weights assigned to the Soil <br /> Behavior Type zones or from a user defined unit weight profile <br /> Details regarding the interpretation methods for all of the Interpreted parameters is given in table 1 The <br /> appropriate references referred to In table 1 are listed in table 2 <br /> ' The estimated Soil Behavior Type is based on the charts developed by Robertson and Campanella shown <br /> in figure 1 <br /> Table 1 CPT Interpretation Methods <br /> Interpreted Description Equation Ref <br /> Parameter <br /> ' Depth mid layer depth IT __ __ _ _ __ _ <br /> AvgQt Averaged corrected tip(Qt) w <br /> AvgQt=1�Qt, <br /> I <br /> AvgFs Averaged sleeve faction(Fs) <br /> AvgFs= E Fs, <br /> AvgRf Averaged friction ratio-(Rf)- <br /> n � <br /> AvgRf=1000// . AvgFs <br /> ' <br /> - AvgQt AvgUd Averaged dynamic pore pressure(Ud) 1 <br /> AvgUd=—Y_Ud, <br /> n <br /> ' SBT Sod Behavior Type as defined by Robertson and Campanella <br />